Both natural and synthetic polymers, including homopolymers and copolymers, which are both biocompatible and absorbable in vivo are known for use in the manufacture of medical devices that are implanted in body tissue and absorb over time. Examples of such medical devices include suture anchor devices, sutures, staples, surgical tacks, clips, plates and screws, drug delivery devices, adhesion prevention films and foams, and tissue adhesives.
Natural polymers may include catgut, cellulose derivatives and collagen. Natural polymers typically absorb by an enzymatic degradation process in the body.
Synthetic polymers may include aliphatic polyesters, polyanhydrides and poly(orthoester)s. Synthetic absorbable polymers typically degrade by a hydrolytic mechanism. Such synthetic absorbable polymers include homopolymers, such as poly(glycolide), poly(lactide), poly(ε-caprolactone), poly(trimethylene carbonate) and poly(p-dioxanone), and copolymers, such as poly(lactide-co-glycolide), poly(ε-caprolactone-co-glycolide), and poly(glycolide-co-trimethylene carbonate). The polymers may be statistically random copolymers, segmented copolymers, block copolymers or graft copolymers.
Several injectable, bioabsorbable liquid copolymers suitable for use in parenteral applications as well as soft tissue repair or augmentation materials in animals have been described. These liquid polymers contain lactone repeating units, including ε-caprolactone trimethylene carbonate, ether lactone, glycolide, lactide, p-dioxanone, and combinations thereof. These liquid copolymers, however, are slow to degrade, taking over six months to be absorbed by the body.
Alkyd-type polyesters prepared by the polycondensation of a polyol, polyacid and fatty acid are used in the coating industry in a variety of products, including chemical resins, enamels, varnishes and paints. These polyesters also are used in the food industry to make texturized oils and emulsions for use as fat substitutes.
There is a great need for polymers for use in drug delivery and medical devices that permit solvent-free processing techniques in preparation of medical devices and compositions and that biodegrade within 6 months.